Conventionally, in a timepiece including a wheel train which rotates by driving a motor, for example, in an analog electronic timepiece, a wheel train is rotated by driving a rotor constituting a step motor. Rotor includes rotor magnet and rotor pinion (in a rotor this refers to parts other than the rotor magnet, and similarly hereunder). For example, gear wheels such as a rotor pinion, a fifth wheel-and-pinion, a fourth wheel-and-pinion, a third wheel-and-pinion, and a center wheel-and-pinion, constitute the wheel train. Moreover, conventionally, in a timepiece including a wheel train which rotates by the force of a mainspring, for example, in a mechanical timepiece, the wheel train is rotated by rotation of a barrel drum including mainsprings. For example, gear wheels such as a barrel complete, a second wheel-and-pinion, a third wheel-and-pinion, a fourth wheel-and-pinion, and an escape wheel-and-pinion constitute a wheel train. A gear wheel has a gear wheel section and a shaft section. Supporting members such as a main plate, a wheel train bridge, and a second bridge are provided with bearing section. The shaft section of the gear wheel is rotatably supported by the bearing section.
The main plate, the wheel train bridge, and the second bridge constitute supporting members. The main plate, the wheel train bridge, and the second bridge are formed from a metal such as brass. The construction of the bearing section of the wheel train is such that a ruby hole jewel and a copper alloy bush are formed separately from a main body of the main plate (main plate body), a main body of the wheel train bridge (wheel train bridge body), and a main body of the second bridge (second bridge body) so that the jewel and the pivot frame are inserted into the main plate body, the wheel train bridge body, and the second bridge body with pressure to secure. Or, a bearing hole (pivot hole) constructing the bearing section is formed directly on the main plate body, the wheel train bridge body, and the second bridge body. In either construction, the bearing section of the wheel train is lubricated with lubricating oil (oil for timepiece).
However, due to vibration when using a timepiece or impact on the timepiece, there is the likelihood such that the lubricating oil is dispersed, with the unnecessary lubricating oil being adhered to tooth surfaces of the gear or a hair spring, causing deterioration of the timepiece. Moreover, due to the temperature variation in the environment for using the timepiece, there is the likelihood such that the viscosity of the lubricating oil varies, greatly affecting the basic functions of the timepiece, such as increasing the power consumption, decreasing the oscillation angle of the balance complete, or the like. Moreover, in order to prevent the lubricating oil from being evaporated or dispersed, if a special bearing structure such as “combined jewelled bush” including the cap jewel and the jewel is used, or the bearing section is provided with an “oil collection section”, the bearing structure becomes complex, causing the problem of high cost of the timepiece.
Furthermore, in the case where a ruby jewel is used, there is a problem in that, for example, similarly to a jewel constituting the bearing sections above and below the barrel drum wheel, as the ratio (outer diameter/hole diameter) of the jewel comes closer to 1.0, the likelihood of breaking the jewel is increased. For example, referring to FIG. 11, in a conventional automatic winding timepiece, a oscillating weight shaft 812 is driven into a transfer bridge 810. An inner ring 822 is screwed into a male screw section of the oscillating weight shaft 812. The inner ring 822 and a ball stopper ring 820 rotatably support an outer ring 826 through a plurality of balls 824. A weight (not shown) is fixed onto the outer ring 826 through a rotation plumb body 828. A retainer 830 locates the plurality of balls 824 in the position between the inner ring 822, the ball stopper ring 820, and the outer ring 826. A upper hole jewel bush for fourth wheel-and-pinion 814 is driven into the central hole of the oscillating weight shaft 812. A fourth upper jewel 816 is driven into the central hole of the upper hole jewel bush for fourth wheel-and-pinion 814. The upper hole jewel bush for fourth wheel-and-pinion 814 rotatably supports an upper-shaft section 840b of a fourth wheel-and-pinion 840. As shown in FIG. 11, in such doubly driven configuration where the jewel frame is driven into the supporting members and the jewel is driven into the jewel frame which is driven into the supporting members, there is a high likelihood of breaking the jewel when the jewel is being driven in to the jewel frame. The likelihood of breaking the jewel occurs remarkably particularly when the part where the jewel frame is being driven and the part where the jewel is being driven into the jewel frame are approximately on the same plane.